Tidal Series: Can Tidal Energy Make Nova Scotia Green?

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Briefly describe your background as it pertains to the study of tidal energy.

I am a professor in the Department of Mathematics and Statistics who uses mathematical models and numerical simulations to do research in physical oceanography and fluid dynamics. For the past eight years, I’ve led a team of Acadia students and research assistants that have researched the potential of tidal energy in the Bay of Fundy. Working in collaboration with other universities, several Nova Scotia businesses, and the Nova Scotian and Canadian governments, our team has calculated the size of the resource and determined the best possible locations for turbines. And along the way, we’ve also learned an incredible amount about the tides of the Bay of Fundy.

What is the practical resource of tidal power in the Bay of Fundy?

Most of you are familiar with the incredible tides of the Bay of Fundy: the highest in the world, with a tidal range reaching 17 metres in the Minas Basin, and somewhere between 100 and 160 billion tonnes of water flowing in and out of the bay with each tide. The flow through Minas Passage during a strong flood tide exceeds the flow of all the rivers in the world combined, with the water’s speed exceeding 5 m/s. There must be a ridiculous amount of energy in these tides and tidal currents!

In reality, the energy we can extract is actually rather modest. The potential energy in raising the water of

Cape Split with Minas Passage in the background. The turbines are set to be installed in the passage near Parrsboro. Photo taken by Dr. Richard Karsten.

Cape Split with Minas Passage in the background. The turbines are set to be installed in the passage near Parrsboro. Photo taken by Dr. Richard Karsten.

Minas Basin by 15 metres is very large (1015 J) but this process takes place over 6 hours and we can only generate power from a difference in water depth–so, at best, we can only take advantage of half of the tidal range. All of this reduces the average power we could theoretically generate from the Minas Basin tides to roughly 10,000 MW. That’s less than half the generation capacity of the world’s largest hydroelectric dam, the Three Gorges Dam in China. Despite having water flow greater than all the rivers in the world, the power potential is that of just one hydro dam (but it would be very large!). It is also four times the size of the current electricity-generating capacity of Nova Scotia, so it is still an important amount for our local energy concerns.

The potential that exists within the Bay of Fundy tides has been recognized for at least a century, with a recent focus on tidal turbines, which act much like wind turbines – using fast-flowing currents to turn turbines that generate electricity. We have calculated that such turbines could in theory extract 7500 MW from the fast-flowing currents of Minas Passage, which is close to the theoretical limit. More importantly, we found that 2500 MW of power could be extracted from the flow while reducing the height of the tides by only 5%. These numbers were very important to me – they meant that the research was worth continuing and that tidal turbines placed in Minas Passage had the potential of meeting Nova Scotia’s electricity needs. But, they also meant that tidal energy wasn’t a global or national energy solution and (unfortunately) there would be no Nobel Prize.

The hard work still remains. How can we change these theoretical calculations into electricity? Renewable energy has an unfortunate history of promising large amounts of power, but producing much less. The province of Nova Scotia has set a goal of deploying tidal turbines with an installed capacity of 300 MW, both a modest and an ambitious goal. This will require the deployment of approximately 150 turbines in Minas Passage – a considerable challenge, since only a handful of turbines have been deployed throughout the world. And, given that the turbines will have a capacity factor of maybe 50%, they will produce less than 10% of Nova Scotia’s electricity needs. By our calculations, 150 turbines would have only a small impact on the tides, roughly reducing the high tide in Wolfville harbour by 5 cm. But we are still a long way from getting there.

It’s also worth noting that tidal energy isn’t just about large, commercial-scale projects. In fact, most of our research has been in collaboration with small Nova Scotia businesses, in particular Fundy Tidal Inc. (FTI), a community-owned company that is trying to bring tidal energy to Digby Neck. FTI’s goal is also to keep the benefits of developing tidal energy in the local communities, something that I support so strongly that I became a shareholder in FTI.

Should Nova Scotia pursue tidal energy as an energy source?

In short: yes. But we still need to do a considerable amount of work to determine if we can do this in an efficient, economical and environmentally friendly manner. On what scale should tidal energy be developed? We don’t know yet, but if we are going to reduce our use of fossil fuels, say by using electric cars, we need to substantially increase our sources of renewable electricity. And there is only one form of renewable energy in Nova Scotia that is among the world’s best opportunities, where we can be a world leader in its development. Could tidal energy bring both types of green to Nova Scotia? We have to at least try.

For more information on tidal energy efforts at Acadia, visit http://tidalenergy.acadiau.ca/.

 

Richard Karsten

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